There is no universally best weight independent of weave, construction and the conditions in which you will wear the suit. Ask for a comparison of specific cloths rather than choosing the lowest gram figure.
For example, Vitale Barberis Canonico describes its Greenhills cloth as 230 grams per metre while also emphasizing its compact structure. That combination illustrates why weight alone is an incomplete selection rule. (vitalebarberiscanonico.com)
Use this consultation brief:
- Where will the suit be worn most often—not merely where it is made?
- How much time will be spent outdoors versus in air-conditioned buildings?
- Is the priority formal appearance, travel performance, low weight or frequent wear?
- How do the proposed cloths differ in weave, feel and drape?
- What lining and jacket structure accompany each choice?
Do not confuse fabric weight with a Super S number. Woolmark's explanation describes increasing Super S numbers as indicating finer wool fibers; it is not a temperature rating. (woolmark.com)
Our recommendation is to compare two or three actual swatches and written specifications. Confirm whether the weight is expressed per square metre or per linear metre before comparing numbers from different books.